Its main change is MAC's Catalina compatibility.So if you must have Catalina get it.BUT remember that Catalina is flaky with ALL earlier versions of SketchUp and they won't be getting updated.So if you use v2017/2018 you can't step up to Catalina.

Catalina has also broken lots of other common applications, so you might want to check what they are, as fixing SketchUp might only be one step down along road !!

Catalina has broken many apps !The latest SketchUp v2019.3 [available but not widely advertised yet!] addresses most known issues, but I understand that it still suffers from an 'undo/redo' bug, and that needs fixing directly by Apple !

@Euadorian what kind of problem with Audacity are you seeing? If it is being rejected as 32-bit, you need to update to the latest release (2.3.2) which is 64-bit. However, there is known issue with access to certain input devices such as the microphone. They are looking into it. See this link for a temporary workaround: